Follow-up system with two circuits alternately supplied with constant and variable currents



Nov. 22, 1949 c. R. MIKOLIC 2,489,241

- FOLLOW-UP SYSTEM WITH TWO CIRCUITS ALTERNATELY SUPPLIED WITH CONSTANT AND VARIABLE CURRENTS Filed March 8, 1947 INVENTOR 12mm @wmwm TTORNEY Patented Nov. 22, 1949 FOLLOW-UP SYSTEM WITH TWO CIRCUITS ALTERNATELY SUPPLIED WITH CON- STAN T AND VARIABLE CURRENTS' Charles R. Mikolic, Milwaukee, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application March 8, 1947, Serial No. 733,332

2 Claims.

This invention relates in general to improvements in follow-up systems, and more particularly to electrical means for causing continuous or oscillatory rotation of a receiver member in response to continuous rotation of a transmitter member.

Remote control of the rotation of a receiver member provided with windings may be effected by connecting the windings with a source of current through a transmitter member comprising a single resistor and contact means actuable in variable engagement with different portions of the resistor at selected positions. To render the system as simple as possible, the receiver should be provided with two windings, two being the minimum number of windings which can be used. The receiver preferably should also be provided with a magnetic core in which magnetization reaches the saturation range, both to reduce the dimensions of the receiver and to insure production of a substantially uniform torque by means of non-uniform currents. To reduce the number of sections of the resistor to a minimum for a given number of steps in the receiver movement, all resistor sections are connected in series and the contact means are so arranged that the connections of the receiver windings with the resistor are varied alternately rather than simultaneously.

Proportionality between the transmitter and receiver movements may then be insured by causing the receiver currents to vary one at a time in proportion to the tangent of an angle proportional to the displacement of the contact means from a predetermined position. When the receiver is to have an oscillatory motion, such motion may be obtained by inserting suitable rectifying means in the connections between the contact means and one of the receiver windings.

It is therefore an object of the present invention to provide an improved electrical system for causing remote actuation of a rotatable receiver, the system including contact means associated with a single resistor having the least possible number of sections for a given number of steps in the receiver movement.

Another object of the present invention is to provide an improved electrical system for causing remote actuation of a rotatable receiver in which the receiver torque is not appreciably affected by variations in the voltage of the source supplying the system.

Another object of the present invention is to provide an improved electrical system for causing remote actuation of a rotatable receiver in which the currents through the receiver windings are varied alternately.

Objects and advantages other than those above set forth will be apparent from a consideration of the following description when read in connection with the accompanying drawing, in which:

Fig. 1 diagrammatically illustrates the arrangement and connections of the transmitter and the receiver of a follow-up system embodying features of the invention;

Fig. 2 is an end view of the receiver illustrated in Fig. 1 showing the end connections of only one of the receiver stator windings;

Fig. 3 is an end view of the receiver illustrated in Fig. 1 showing the end connections of the other stator winding only; and

Fig. 4 is a diagram of the variation of the receiver currents during a revolution of the transmitter contact means.

Referring more particularly to the drawing by characters of reference, numeral 6 generally deslgnates a rotatable signal receiver to be remotely actuated. Receiver 6 comprises a stator member I and a rotor member 3. One of the receiver members, stator l for example, is provided with a pair of duplicate overlapping windings l0, ll. Each of windings I 0, I I may define one or more pairs of poles, and the two windings are disposed with their axes displaced by ninety electrical degrees with respect to each other. The conductors of windings H), II are disposed in slots distributed around the bore of the magnetic core of stator l. The distribution of each stator Winding may be uniform but is preferably made sinusoidal, the number of conductors in each slot then being proportional to the sine of the angle defined by radii passing through the slot considered and through a reference point.

Rotor 8 may be of any suitable known type and is represented as a block of magnetizable material defining a pair of salient poles. Rotor 8 may be unmagnetized but is preferably magnetized either permanently or by energization of a suitable winding (not shown) disposed thereon. If rotor 8 is without polar projections it must be magnetized either permanently or by means of a suitable magnetizing winding. The rotor may also be provided with a pair of variably energized windings similar to stator windings I0, ll.

Rotor 8 is mounted on a shaft l2 connected with any device to be remotely actuated. Shaft l2 may serve, for example, to actuate a device requirin substantially no torque, such as a pointer 13 to be moved over an indicating dial l4. Shaft 12 may also be used to drive a device requiring exertion of a substantial torque, such as a valve l5 for controlling the flow of fluid through a conduit.

To cause rotation of shaft I2, windings I0, I l are variably energized from a suitable source of current conventionally represented as a battery l6, through a signal transmitter generally designated IT. The transmitter comprises a single resistor 58 having its terminals connected with the terminals of battery it, and contact means actuable in variable engagement with different portions of the resistor at selected positions. All portions of resistor 13 are connected in series Toetween the resistor terminals.

The contact means comprise; a circula contact structure preferably arranged on an insulating panel (not shown) similarly to the contact structures of so-called face plate rheostats. The contact structure preferably comprises two contact segments 20, 2i severally connected with the terminals of battery Hi and extending over opposite arcs of slightly more than 90". Two sets of contact studs are disposed intermediate seg ments 2|, and the corresponding studs of the two sets are connected in pairs with a plurality of taps of resistor l8. The studs may comprise a pair of studs 22, 23 disposed on opposite radii. Studs 22, 23 are preferably connected with a mid tap of resistor l8 but may simply be connected together or even left unconnected.

The contact means further comprise pair of brushes 24, 25 disposed on opposite radii. Brush 24 is connected with one terminal of wind ing Iii through a conductor 26 of any suitable form, a brush 2-1, and a slip ring Brush 25 is similarly connected with the other terminal of winding l through a conductor a brush 32, and a slip ring 33.

Further brushes 34, 35 are disposed on opposite radiiat 90 to the radii of brushes 2d, and are connected to the terminals of winding ii. The connections of the two pairs of brushes may be similar if continuous rotation of the brushes is to result in continuous rotation of rotor 8. To render rotor 8 operable for either continuous or oscillatory movement in response to continuous rotation of the brushes, brush 3 3, is connected with winding l I through a conductor 36, a brush 3], and a slip ring interrupted at the radii of studs 22, 23 to form two half-rings S8, 36. Likewise brush 35 is connected. with windin 1! through a conductor 41, a brush and a slip ring interrupted at the radii of studs 23 to form two half-rings E3, M.

Half-rin s 39, 43 are severally connected with the terminals of winding I l. Half-ring 39 is also connected either with half-ring 38 or with halfring M, half-ring 43 being correspondingly ccnnested either with half-ring 44 or with half-ring 33. While the half-ring connections are generally eifected permanently in the particular manner resulting in the desired movement of rotor 8, such connections are shown effected through a switch 45 to render the drawing clearer.

All. brushes are supported by a suitable insulatin brush rigging, which is not shown to simplify the drawing. The brush rigging is mounted on a shaft 46, which may be given any desired rotational movement by suitable actuating means suchas a hand lever 41, to cause all the brushes to. be rotated. simultaneously to a uniform extent.

When switch 45 is inthe position shown, halfrings 38, 39 are interconnected so as to function as a continuous-slip ring, and half-rings i3. 44 likewise serve as a continuous slip ring. The brushes being in the position shown, windings ill. are directly connected with the terminals of battery Hi to receive therefrom equal currents of' predetermined maximum value.

The receiver windings are preferably so dimensioned that the current through one winding alone is sufficient to cause magnetic saturation of the rotor core or of the stator core. The total magnetic flux produced in the receiver by one winding then has a value which is substantially unaffected by moderate variations in the voltageof, battery 18 and by variations in the flow of currentthrough the other winding. The magnetic flux in stator 1 results from the joint magnetomotive forces of windings l0 and H and accordingly causes rotor 8 to assume a position of 45 to the axes of the windings.

Assume that-lever 31 is rotated clockwise from the position shown into a position at therefrom. During such movement, brushes 35 slide over segments 20, 21 respectively and tain winding ll connected with the terminals of. battery 56 to receive constant current therefrom. t the Sametime; brush 24 moves from segment 20 over one set of contact studs includin stud to reach segment 2 l, and brush 25 moves from segment 2! over the other set of studs including stud 23 to reach segment 28. Winding ii] is thus connected with battery I 5 through a variable portion of resistor l8 and is connected in parallel with'the balance of resistor l8, whereby the voltage impressed on winding H] i reversed in polarity while first being decreased and then again increased in a predetermined number of steps depending upon the number of contact studs.

The resistance'of the different portions of resistor is connected between different contact studs is so distributed that the current through winding ll varies in proportion to the tangent of an angle-proportional to the angle comprised between the radii of brush 24 and of stud 22. With the transmitter arrangement illustrated in Fig. 1 the factor of proportionality between such angles is equal to unity. Designating by 2B the resistance of resistor l8 and by 2mR the resistance of each of windings H), l I, the resistance left of the resistor portion included between stud 22 and another stud distant therefrom by an angle at may be found from the relation:

The factor It varies from 1 to +1 when x varies from -45 to +45. If the resistance of windings H], II is very large relatively to resistance R, the above relation may be reduced to the approximate simplified form k=tan x The current through winding ID accordingly has the variable value E tan r/ZmR while the current through winding H has the constant value E/ZmR. As a result'of the arrangement of windings [0, II at 90; themagnetomotive forces thereof combine vectorially to cause the flux induced in the receiver air gap to shift by an angle equal to the angle of displacement of the brushes from the position shown.

Althoughthe resultant of the two receiver currents varies in magnitude, the receiver flux will have a substantially constant value if the re-- ceiver magnetization reaches the saturation range. The flux shift causes rotor 11 to describe the same angle as the brushes, as if the current of winding l0 hadremained constant and windings H], II had been shifted by the same angle as the brushes. During movement of rotor 3, the friction of the mechanism of valve l5 causes the rotor to lag behind the transmitter brushes. When the-receiver flux issubstantially constant,

the-angle of-lag of rctor-fl issubstantially uniform at all positions of the rotor and may be accounted for.

Further rotation of lever 4'! by 90 in the clockwise direction causes brushes 24, to slide over segments 2|, '20 respectivel to supply constant current to winding I0. Brushes 34, then travel over the contact studs to gradually reverse the voltage impressed on winding H to cause the flux of receiver 6 to shift another 90. Continued rotation of the brushes thus causes alternate impression on windings l0, ll of a constant voltage during rotation of the brushes over substantially 90, and of a gradually variable voltage during further rotation of the brushes over 90.

Each winding thus alternately receives a constant current of predetermined value sufiicient to cause magnetic saturation of the associated core, and a current varying in steps between zero and the same value but of reversin polarity. It will be observed that the number of taps to be provided on resistor i 8 is smaller than one quarter the number of steps of each revolution of rotor 8.

During uniform rotation of the transmitter brushes, windings I0, ll receive non-sinusoidal alternating currents relatively shifted in phase by 90. The variation of the current through winding I0 is represented by curve 48 in Fig. 4, and the variation of the current through winding I l is represented by curve 49.

When switch is reversed from the position shown, half-rings 38, 39, 43, 44 cooperate with brushes 31, 42 to form rectifying means in the connections between brushes 34, 35 and the terminals of Winding H. The rectifying means thus obtained are of the synchronous mechanical type, but it will be understood that any other type of rectifier may be utilized instead. As a result of the presence of the rectifying means, the connections of winding I l are reversed every time brush 34 travels over stud 22 or stud 23. The current of winding H is no longer an alternating current represented by curve 49 and is instead a rectified current represented by curve in Fig. 4. Curve 50 differs from curve 49 by reversal of the negative portions thereof.

It will be observed that lever 41 may be brought into two positions wherein brush 34 engages one of studs 22, 23 and brush 35 engages the other of the two studs, which are at the same potential. Winding H is then without current, its current then being represented by either of the two points of zero ordinate of curve 50. If lever 41 is rotated 180 between the latter two positions, the variation of the currents through windings l0, II will be the same regardless of the direction of rotation of lever 41, and rotor 8 will rotate 180 in one direction regardless of the direction of the rotation of lever 41. Further 180 rotation of lever 41 causes the receiver currents to return to their original values to cause rotor 8 to reverse its motion and return to its original position.

Continuous rotation of lever 41 in either direction results in oscillatory movement of rotor 8 over an angle of 180. Lever 41 may thus be used simultaneously to control one device through receiver 6 in response to the amplitude only of the rotation of the lever, and to control another device directly connected with shaft 46 in response to both amplitude and direction of the rotation of the lever.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a control system supplied from a source of electric current, the combination of a signal transmitter comprising a single resistor and contact means actuable in variable engagement with different portions of said resistor at selected positions, and a signal receiver comprising a stator member and a rotor member, one of said members being provided with two windings having "their axes relatively displaced by ninety electrical degrees, means connecting said windings where said contact means for impressing alterhating voltages on said windings in response to movement of said contact means, and rectifying means in the connections between said control means and one of said windings to cause said rotor member to be actuated in response to the amplitude of the displacement of said contact means from a predetermined position and to be unresponsive to the direction of said displacement.

2. In a control system supplied from a source of electric current, the combination of a signal transmitter comprising a single resistor and contact means actuable in variable engagement with different portions of said resistor at selected positions, and a signal receiver comprising a stator member and a rotor member, one of said members being provided with a magnetic core and with two duplicate windings having their axes relatively displaced by ninety electrical degrees, a circuit connecting one of said windings with the terminals of said source, each of said windings having a predetermined impedance to cause one of said windings to receive from said source current of predetermined value sufficient to cause magnetic saturation of said core, the other of said windings being connected with said source through said contact means and a variable portion of said resistor, the said different portions of said resistor all being connected in series and so distributed between selected positions of said contact means as to cause the current through the said winding connected therewith to vary between zero and said predetermined value in proportion to the tangent of an angle proportional to the displacement of said contact means from a predetermined position,

whereby the magnetic flux produced in said core is caused to shift by an angle proportional to the first said angle while retaining a substantially constant value.

CHARLES R. MIKOLIC.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 798,236 Usener Aug. 29, 1905 2,300,220 Hempel Oct. 27, 1942 Certificate of Correction Patent No. 2,489,241 November 22, 1949 CHARLES R. MIKOLIO It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 20, for the word Where read with; line 23, for control read contact;

and that the said Letters Patent shouldbe read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 14th day of March, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommz'ssz'cner of Patents.

Certificate of Correction Patent No. 2,489,241 November 22, 1949 CHARLES R. MIKOLIC It is hereby certified that errors appear in the printed specificationof the above numbered patent requiring correction as follows:

Column 6, line 20, for the word Where read with; line 23, for control read. contact;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofice.

Signed and sealed this 14th day of March, A. D. 1950.

THOMAS F. MURPHY,

Assistant Uommz'ssz'cner of Patents. 

